Fogging.
If you sit in your darkroom for thirty minutes with the safelight off, do you see anything? Leaks of light, red lights on power adapters, indicator-lights on equipment etc.
Is there any reflective surface near your enlarger easel (eg. next to a white wall), or a light-leak from the enlarger head, when you are printing?
Is your paper fresh - not newly bought (it may have been on the shelf in the shop for four years next to a radiator, for example), I mean less than couple of years old and well stored.
Develop+stop+fix one sheet of unexposed paper in total darkness. Fix one sheet of unexposed paper in total darkness. Are they exactly the same colour? If not, you have fogged paper.
Note the specifications for the Edu / Foma paper require a dark-red safelight bulb. Use it, not orange or green or a light not manufactured as a safelight (eg. a red christmas tree light?!). Make sure that you use a bulb wattage specified for the enclosure, or lower than the maximum. Bouncing the safelight off the ceiling, instead of having it pointing towards the working area, may help in a small darkroom as an alternative to using a smaller wattage bulb. Remember that safelight filters can fade and that a second hand lamp may have been used for decades.
If all the above quick checks seem superficially ok, do a thorough safelight check. Use the Kodak style of check with paper exposed to the maximum non-visible exposure. Don't expect that leaving a piece of paper out for a couple of minutes and then developing it will indicate safety.
Check that your developer really is mixed according to the instructions. It has been known for people to accidentally use a stock-solution, instead of diluting it for use.
Remember that Foma paper can work perfectly adequately so, as you have noticed, there is something going wrong in your darkroom ! Please keep us informed of what you find, as it may help the next person with a "strange" darkroom problem who looks in Apug for an answer.