Help Needed. Issues with Tank.

[DreaminginBlue]

So I went to go check on the tank in my godmother's office in anticipation of the arrival of some shrimp next week. I've been busy and her office is a distance away, so I haven't been able to check on it since setting it up. I wasn't worried about it. I'd seeded it with a mature sponge from my tank and I was positive it'd cycled. It had an ammonia source and everything, and it had been weeks.
Well, I took one look at the tank and cringed. The spiderwood was covered in some weird white slime. The wisteria and water sprite, in some areas, had melted into brownish mush. The java moss looked practically dead, with only small bits of green showing through. I took readings and nitrite and nitrate were at 0. Ammonia was at .50.
I can't understand what happened? Did it not cycle? Did something restart the cycle? How could a seeded tank with an ammonia source not cycle? What is the white stuff and why are the plants melting at such an alarming rate?
So. Frustrated.
She dumped a whole bottle of bacterial starter into the tank yesterday, so I'm not sure that'll help. I took the lone fish out of the tank, so there isn't a live ammonia source, but I'm sure all that plant gunk breaking down is producing quite a bit.
I'll attach pics, but unless I can get this fixed by the end of the week I'm going to have to upend my plans and put the shrimp into my ten gallon at home.

 

[TMaier]

Stuff like this can be so frustrating! It sounds like you did everything right.

 

[Toad]

Tbh having stuff grow out of driftwood in the beginning is pretty normal in my experience. What fish was your ammonia source?

I'm guessing the plants went into a melt/shock and started rotting, and that jumped your ammonia beyond the levels your media could handle right now.

 

[DreaminginBlue]

I had my lovely betta, Atlas, in there. We went on vacation and I didn't want to leave him alone, he loves attention and I worried about him being fed so he went to stay at her work so her coworkers could feed him. I wasn't worried about the tank not being cycled, I was certain it had been. I seeded it with a sponge from my C3, and the bioload there is way more than a betta, so I figured he'd be fine.
I thought that might be the case, Toad, but the nitrate reading worries me. I thought in cycled tanks, you'd always see nitrates? Either I read it wrong and there are some, I did the test wrong (I swear I shook that vial for a minute), or the plants are sucking it all up?
Thanks, TMaier, I was sure I had and then I saw this disaster and felt awful. She just wants to enjoy her first fish tank and she had no clue anything was wrong. I feel like I've failed her, but she's not upset. She just wants to help me get this fixed.

 

[coralbandit]

I believe for nitrAtes you need to shake the bottle of the #2 reagent for 30 seconds before you add the drops to vial. Whatever is in it is a solid that settles to the bottom...
Also possibly the plants used up the nitrates as they prefer them over ammonia.
This could also possibly explain the poor plants?
I was told plants can easily take over a month sometimes to acclimate to new water sources...

 

[DreaminginBlue]

Thanks, coralbandit. I've and plants melt before, but never on this scale.
I remember shaking the bottle for 30 seconds, then shaking the vial for a minute, but maybe I messed up somehow.
I'm hoping it's cycled, but I'm not willing to chance it with the shrimp so they'll have to go in the ten gallon for now.