compression changed irregulary

[xka24detx]

i checked compression today after overheating and seeing alot of smoke come out of cylinder #4 head area the results are way off from when i checked it when i first got the car, i know its boud to change over time, but this change is confusing me... i dont know if something is blown, not sealing right, etc...
i havent tried the putting the oil in the cylinder test in #4 yet to see if it raises, just wanted to get your opinions

before
1=175
2=180
3=175
4=180

Now:
1=190
2=195
3=175
4=165

and to just add as a note #2, 3, 4 plugs looked to be burning good light greyish, but #1 was yellow, literally yellow, and on pdm's site on "how to read plugs" they dont say anything about yellow plugs