Problem with growing HEK293 - (Apr/09/2017 )

I have noticed my cells are growing slower than regular a week ago and I suspect about contamination.So I did staining & imaging yesterday using hoescht 33342 dye and noticed abnormal shape of nucleus in my cells. Does anyone have any idea what could be causing this? I prepared my medium on 22nd of February with following recipe. Plus I was doing transient transfection to my cells previously gfp fused plasmid that I believed to be expressing, however I also noticed yesterday that my cells without any transfection are emitting flourescence under gfp  spectrum too. I have no prior knowledge working with cell cultures so any insight would be appreciated. TIA

The cells look fairly normal - nuclei are generally not round in adherent cells.

Growth slowing is another matter - if you can tell us what you have done with the cells and anything that might have changed (e.g. different lot of FBS recently), we will have a better idea of what might be going on. 

There is always some auto-fluorescence with cells in the green channel - and it is can be a big problem as it is almost impossible to remove. If you are looking for a faint change or minor differences in localization it might be better to go for a RFP or YFP. 

I normally don't use media for much more than a week.  If you're still using complete media from 6 weeks ago, that's not a good thing.  What seeding density are you passaging them and what is the media formulation?

Do a mycoplasma test.  In my hands, 293T cells are very sensitive and greatly reduce proliferation (and increase adherence) with contamination.  Zooming in, I can find a few cells with cytoplasmic dots, but DAPI is the least sensitive way to detect mycoplasma.