What a lovely block!
When you are sewing your HST together, make sure you are using the 1/4" seam allowance from the edge of the fabric...instead of being straight on I tend to slightly "swing" into my stitching at the beginning and end of the seam..this little bit skews the seam allowance. Mindlessly sew a few pairs of fabric squares together...do you see a little curve in your stitching? If so this could be the problem. (Ask me how I know!) I think this is more noticeable with HST because the point isn't right.
So how to avoid this swinging? Sit squarely in front of your needle so that you are feeding the fabric in squarely. At the end of the seam chain piecing another unit through..this helps me keep the pieces in straight alignment. One of the reasons I like Bonnie Hunter's leaders and enders technique is because I always have something to chain piece and keep me straight sewing.
https://quiltville.com/leadersenders.shtml
This is a good tutorial, but notice that all of the seam allowance is nice and even.
https://www.connectingthreads.com/tu...Pin__D103.html
Your are coming along beautifully...enjoy this new hobby. I hope it will give you a lifetime of pleasure as it has given me!