I've been away for a week and someone has been feeding my fish whilst I was gone.

I came home to find these white furry nodular growths over all my plants. It wasn't there a week ago.

I assume this is some sort of algae, or fungus but it's not one I recognise.

Tank is a very well established 60L tropical tank with around 10 inches of mixed community fish - raspboras, dwarf corys and Endless plus a few small shrimp. I did a 20% water change the day I went away.

I've tested this morning and the results are

pH 7.4
Ammonia 0.25 ppm
Nitrite 0.25 ppm
Nitrate 160 ppm Eek!

I've also noticed today the temp is showning low @69C so ithink my heater is not working as it should do.

I've done a 40% water change to try to bring the nitrate down.

What else do I need to do to get this down urgently and to treat the fungal/algal bloom?

Any help much appreciated.

Looks like your sitter has been over-enthusiastic with the food. Those grey "nodules" appear to be food particles growing mould/fungus. Remove them with your syphon while changing water, which is what you need to do to get the ammonia/nitrite/nitrate down.