What are you feeding? a good quality diet along with the water changes can make a world of difference my Angels and Angelicous botia loaches have grown like weeds with with a high protein diet.. I feed once to twice a day b/c the two loaches i got looked pretty malnourished when i got them.. so trying to fatten them up and grow the angels pretty fast! i rotate between Omega 1 Color enhancing tropical flakes, Frozen brine shrimp, shrimp wafers for the loaches, freeze dried blood worms and peas once a week to keep their gi system in check(high protein diet can lead to constipation and blockages)!
I probably feed a little more than recommended but but my fish have grown very fast with my current feed schedule.. but remember with extra feedings comes the need for more frequent water changes.. i do about 30% every three days +or- a day.. and all my levels stay good nitrates around 5-10 amm. nitrite =0
Also temp plays a role lower temps will slow down metabolism and slow growth, where as higher temps with speed up metabolism and growth, Also if you have a lot of current in the tank esp for the angels that's going to stress them a little more and they will expend more energy and will tend to grow slower