Fired After Requesting Fmla Forms?

I informed my boss last weekend that I needed to take this week off because I had some medical testing to be done.

The labs didn’t come back great, so I requested FMLA paperwork on Tuesday just in case I needed it, and they sent it back yesterday.

Today, my boss calls me with HR (since I work remote) and lets me know that tomorrow will be my last day.

They said it was because they didn’t hit budget last year and needed to cut cost, but I find the timing awfully suspicious.

Do I have any grounds to stand on, or do I take the measly $7k severance ($130k/yr salary) and just move on?