I see what you're saying but without actual figures it's difficult to say how much is too much.
Your salary may have increased by £90 to her £4-500, but if that still leaves you earning significantly more than her, then the SM is there to redress the balance. Yes, she is now earning more than she was, but if it is still not enough and she is still bearing the brunt of childcare etc then to me, the SM should still stand.
I am now earning an extra £4-500 a month and my ex has only had a modest payrise this year. However, that puts him on around £58k in his professional role, and me on around £12k as i work to fit in around the DCs and his shifts. Whooppee doo.
FWIW my ex is dropping the SM part of his payments in return for me getting 100% equity from the house. I know this is the only way he would agree to it, so I have to take a short-term hit for long-term security.
However, it will mean that he has to take on more of the general expenses, contributing to school trips, shoes, party gifts even when they fall on his weekend etc, which at the moment ALL fall to me. The only thing he currently provides for the DCs is food when they're with him, every other expense is supposed to be covered by his payments.