Yes it could be mould or fungus. I it were still green it would be trying to grow more roots. Water temps are most likely too high,very important. Larger leaves turning yellow at maturity is normal. Burning on top may be light or too much nutrients. Looks like over nutes

Very nice though just tune in your grow and maybe higher ceiling. They look like sativa, maybe indica next time ,it won't get too tall. It's all about learning and tuning in.
Enjoy the bud and next time start a mother and have all females.
LOC NAR on probation Reviewed by LOC NAR on probation on . BOSS'S UNKNOWN WATERFARM GROW A short briefing: I started off with two unknown beans from a good batch I recieved. I planted the beans inside of the rockwool cubes, first. Afterwards, when the roots came out the bottom of the cubes, I then put them inside of the Waterfarm. I'm using a 400 MH and 400 HPS system for lighting. I vegetated for a short period, because of time (flowering limitations). I forgot to keep up with the dates of the pictures, so I have no information on the age of the plant at the time of the Rating: 5