I almost lost my oscars, did lose 2, but had to re-home the other 2. My humbled opinion it sounds like you should change your substrate out (PLEASE make sure your fish are in a separate clean bare bottomed tank with cycled, balanced and stable water) and start cycling your tank using distilled water. It sounds like your water supply may be pre softened/ filtered and have some negative trace elements. I didn't know that my cities water was filtered and softened, this often has horrible effects to your nitrate and phosphate levels, not to mention key trace elements and ph. Starting with distilled water (NOT FILTERED OR SPRING) and keep the chemicals to as minimal as possible. Your planted substrate may be a factor too, especially after about 5 months. Planted tanks require pruning and debris removal, plus plants zap beneficial trace elements and require daily addition of electrolytes and frequent ph monitoring. I can't say my methods are perfect but I can tell you what has worked for me.
For a 29g community tank that is planted I'd stick with acid tolerant fish, use a substrate specific to planted tanks, if you have any fish with barbels (catfish like whiskers) I would suggest using a layer of fine sand on top- make sure your plants are secured below the sand line and only allow a small amount of sand to cover the upper roots. Fill tank halfway with distilled water (after adding substrate- treat water with conditioner, my faves are amquel+ and seachem prime) use your filter to add the water to keep from disturbing your substrate. Add your plants and decorations. Condition the rest of the water necessary to fill the tank (if using questionable tap water use a water buffer to buffer to 7.0 and make sure there are no metals, etc). MY SECRET TO ÜBER FAST CYCLES- aerate your water thoroughly, use high circulation and start without carbon filters, add instant cycler- strong recommendation for seachem stability or nutracycle. Allow time for the tank to stabilize running a filter with only biofilter medium. Test your water and adjust as needed. Every day for the first week change out at least 25% of the water. On the final day check water parameters, you'll probably find your ph is lowered. I recommend using a ph adjuster using CaCO3, but a buffering agent to 7.0 should work. Do a 50% water change the starting day of your 2nd week, use distilled water. Test and adjust. From here on out just test daily, remove dead plants and leaves and start adding fertilizer daily once your plants are established and remember to top off your water as it dissipates. It's always beneficial to do at least a 10% change every week and at least a 30% larger change once a month. I do 25% changes weekly and a 50% change with substrate management once a month, I maintain my plants daily and regulate light exposure, this helps keep algae down. Oh, using cured driftwood and lava rock to anchor your plants will keep their roots at a lower 6.2-6.8 ph which is ideal for plants that way your water is balanced for your fish and your plants will respond greatly to the lowered ph at the roots. You might also wanna look into freshwater biozyme.. I wouldn't suggest adding a carbon filter until your bb is re established... Algae blooms are better dealt with by water changes and limiting lighting, not chemicals, especially not in a planted tank. A few oto cats as a preventive measure always helps, and they are the most tolerant and smallest algae cleaners I have seen. So there you have it, I hope this helps. Don't give up, it's hard to understand and be successful when you're just learning, just have some patience and take your time to get to know your tank. Melafix and pimafix can help ease discomfort from injuries your fish may have sustained, just make sure the tank is established and stable and don't overdo it, use half doses, change 25% of water after 3 days of treating. Good luck!!
got any other tanks or friends with established tanks? Your Lfs might be gracious enough to give ya a handful if gravel or some media. You can get them cheap @ AngelsPlus.com. I used they're active sponges and skipped the NitrIte phase. Wc,wc,wc... The key to a successful fish in cycle... 
