I noticed that my charges increase yo $90 abd I would like to know the reason for this

Your discounted period mey be expired and you have to pay the regular rate now. If you wish to keep the lower price, you will need another effort. Utilize the 3rd party tool to migrate your data between QBO accounts.

https:// transactionpro.grsm.io/qbo

Once you are ready to proceed, open a NEW QBO account with a current discounted rate. You may get a discounted price for up to 6 months. 

https:// quickbooks.grsm.io/US

https:// quickbooks.grsm.io/us-promo