Could be Mag could be Boron either or I suspect a deficiency. I would change water, run neutral for 24hrs then drain and run normal nutes according to time frame.
1- Your plants will have grown there for absorbing more light and less refraction
2- One hot start would shorten life but not to the extent your figuring
3- Cooking the ballast may have weakened the output.
IMO I would test the light output and see if I had a drop in lumen, lux and PAR reading...
Ill start by saying hello, Im new to this site so if this is posted in the wrong spot please, admin move it elsewhere.
Ok Ive ordered a bloom box from BCNL and before anyone can say anything, its what I wanted for my particular situation at this point in my life. I know its not the cheapest...