Multiband geotiff loading slow in browser

[lanas1234]

Here's the problem: http://www.doctorharapos.com/webMap/geotiff.html

-My geotiff files are ligth, just 4MB

-My process: starting from a ascii esri file I transform it to geotiff using gdalwarp, because I also do a change of projection

-I stack items in groups of 4 geotiff files with gdalbuildvrt

-I add LZW compression with gdal_translate and overviews with gdaladdo

An example of the answer of gdalinfo:

Driver: GTiff/GeoTIFF
Files: mP2_apr_p50.tiff
Size is 2978, 1167
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (-8.830684460645021,42.286367649318294)
Pixel Size = (0.000057568360165,-0.000057568360165)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  COMPRESSION=LZW
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  (  -8.8306845,  42.2863676) (  8d49'50.46"W, 42d17'10.92"N)
Lower Left  (  -8.8306845,  42.2191854) (  8d49'50.46"W, 42d13' 9.07"N)
Upper Right (  -8.6592459,  42.2863676) (  8d39'33.29"W, 42d17'10.92"N)
Lower Right (  -8.6592459,  42.2191854) (  8d39'33.29"W, 42d13' 9.07"N)
Center      (  -8.7449652,  42.2527765) (  8d44'41.87"W, 42d15'10.00"N)
Band 1 Block=2978x1 Type=Int32, ColorInterp=Gray
  NoData Value=0
  Overviews: 1489x584, 745x292, 373x146, 187x73
Band 2 Block=2978x1 Type=Int32, ColorInterp=Undefined
  NoData Value=0
  Overviews: 1489x584, 745x292, 373x146, 187x73
Band 3 Block=2978x1 Type=Int32, ColorInterp=Undefined
  NoData Value=0
  Overviews: 1489x584, 745x292, 373x146, 187x73
Band 4 Block=2978x1 Type=Int32, ColorInterp=Undefined
  NoData Value=0
  Overviews: 1489x584, 745x292, 373x146, 187x73

Any clue of what is happening or what can I do to speed up the loading?

All the best

[lanas1234]

Maybe this has to do with the problem?

I've realized than when I zoom with my mouse wheel the loading/zooming is made at steps while when I use a mouse gesture zooming with my pad everything goes smooth, maybe there's something with the programming of the wheel zooming that can improved or configured in another way?