LED T8 tubes overheating?
I agree; it sounds like a blown ballast to me. As Ed Beal suggests, if the ballast is rapid-start (2 wires per tube end) the imbalance of some LEDs some real fluorescent may have caused it undue stress.  Or perhaps the ballast was starting to get marginal on its own, and using LEDs forestalled the problem until it deteriorated more.
I'd roll it back to real fluorescent and see if that takes care of it; if it does, happy dappy.  Today's real fluorescents are superb in color quality, and electronic ballasts take care of the rest of the undesirable qualities of &quot;That 70's Fluorescent&quot;.  So no need to go LED if it works at that point.
Note that T8 real fluorescent tubes will not work on T12 ballasts or vice versa. They may &quot;half-work&quot; with bad side effects, and will stress out the ballast.